I have an offer for the PwC Flying Start Degree at Newcastle (although i don't think I have gotten the grades to get in...but thats another story.)
This is by far the easiest route as it does not require testing as such. You apply, and if they like you, they will send you a kind of form to fill out, and then they decide again if they want to give you an interview. The interview is an hour long and either with someone from Newcastle Uni or PwC. Then there is a group assessment on the same day which is also an hour long. This is a standard type of group assessment where you are given a scenario and then you have to individually plan something then present to your little group and try and argue for your case (its not as hard as it sounds).
But basically, flying start is the easiest of the ones you listed, then i would say KPMG's testing is notoriously the hardest, but the Deloitte scholar scheme is probably the most competitive. My sister works for Deloitte and trust me, its a good place to be.